Method and apparatus for non-ablative, heat-activated lithographic imaging

Abstract

Methods and apparatus for lithographic imaging without ablation function by irreversibly debonding intermediate printing-plate layers, thereby rendering at least the surface layer removable by cleaning to expose, in an imagewise pattern, an underlying layer having a different affinity for ink and/or an abhesive fluid for ink. In contrast to ablation-type systems, it is unnecessary to destroy a plate layer, thereby reducing power requirements and facilitating increased imaging speeds.

What is claimed is: 
     
       1. A method of imaging a lithographic printing member, the method comprising the steps of: a. providing a printing member including a first layer and a second layer attached thereto, the first and second layers having different affinities for at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink;   b. heating the printing member so as to irreversibly detach, in an imagewise pattern, the first layer from the second layer without substantially ablating the second layer; and   c. removing the first layer where detached from the second layer so as to form a lithographic image.   
     
     
       2. The method of claim 1 wherein the second layer is a metal treated to absorb imaging radiation. 
     
     
       3. The method of claim 2 wherein the metal layer does not undergo phase change as a consequence of heating. 
     
     
       4. The method of claim 2 wherein the metal layer has a surface selected from the group consisting of oxides, carbides and nitrides. 
     
     
       5. The method of claim 1 wherein the printing member further comprises a third layer disposed beneath the second layer. 
     
     
       6. The method of claim 5 wherein the first and third layers have different affinities for at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink, the removing step further comprising removing the second layer as well as the first layer where the first layer is detached from the second layer. 
     
     
       7. The method of claim 1 wherein the second layer is an oleophilic polymer comprising means for absorbing imaging radiation. 
     
     
       8. The method of claim 7 wherein the polymer is a conductive polycarbonate. 
     
     
       9. The method of claim 1 wherein the heating step comprises: a. spacing at least one laser source that produces an imaging output opposite the printing member;   b. guiding the output of the at least one laser source to focus on the printing member;   c. causing relative movement between the laser output and the printing member to effect a scan of the printing member by the laser output; and   d. imagewise exposing the printing member to the laser output during the course of the scan.   
     
     
       10. The method of claim 9 wherein the laser emits infrared radiation. 
     
     
       11. The method of claim 9 wherein the first layer is substantially transparent to the imaging output. 
     
     
       12. The method of claim 1 wherein the first layer is oleophobic and the second layer accepts ink. 
     
     
       13. The method of claim 12 wherein the first layer comprises silicone. 
     
     
       14. The method of claim 1 wherein the first layer is hydrophilic and the second layer is hydrophobic and oleophilic. 
     
     
       15. The method of claim 1 wherein the first layer comprises a heat-responsive polymer which, when subjected to heating, becomes chemically modified to resist reattachment. 
     
     
       16. The method of claim 15 wherein the first layer comprises a heat-responsive polymer that undergoes rapid thermal homolysis. 
     
     
       17. The method of claim 16 wherein the first layer is a block copolymer comprising a polysiloxane chemical species and an acrylic chemical species. 
     
     
       18. A method of imaging a lithographic printing member, the method comprising the steps of: a. providing a printing member including a first layer, a second layer disposed beneath and attached to the first layer and a third layer disposed beneath the second layer, the first layer and at least one of the other layers having different affinities for at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink;   b. heating the printing member so as to irreversibly detach, in an imagewise pattern, the first layer from the second layer without ablating the second layer; and   c. removing at least the first layer where detached from the second layer so as to form a lithographic image comprising regions having said different affinities.   
     
     
       19. The method of claim 18 wherein the removing step further comprises removing the second layer as well as the first layer where the first layer is detached from the second layer. 
     
     
       20. The method of claim 18 wherein the second layer is metal. 
     
     
       21. The method of claim 20 wherein the metal layer does not undergo phase change as a consequence of heating. 
     
     
       22. The method of claim 20 wherein the metal layer comprises at least one of titanium, aluminum, vanadium and zirconium. 
     
     
       23. The method of claim 18 wherein the second layer is polymeric. 
     
     
       24. The method of claim 18 wherein the heating step comprises: a. spacing at least one laser source that produces an imaging output opposite the printing member;   b. guiding the output of the at least one laser source to focus on the printing member;   c. causing relative movement between the laser output and the printing member to effect a scan of the printing member by the laser output; and   d. imagewise exposing the printing member to the laser output during the course of the scan.   
     
     
       25. The method of claim 24 wherein the laser emits infrared radiation. 
     
     
       26. The method of claim 24 wherein the first layer is substantially transparent to the imaging output. 
     
     
       27. The method of claim 18 wherein the first layer is oleophobic and the third layer is oleophilic. 
     
     
       28. The method of claim 27 wherein the first layer comprises silicone. 
     
     
       29. The method of claim 28 wherein the metal layer is titanium. 
     
     
       30. The method of claim 18 wherein the second layer is at least partially unremoved where the first layer is detached from the second layer, the first layer being oleophobic and the second layer accepting ink. 
     
     
       31. The method of claim 18 wherein the first layer is hydrophilic and the third layer is hydrophobic and oleophilic. 
     
     
       32. The method of claim 18 wherein the first layer comprises a heat-responsive polymer which, when subjected to heating, becomes chemically modified to resist reattachment. 
     
     
       33. The method of claim 32 wherein the first layer comprises a heat-responsive polymer that undergoes rapid thermal homolysis. 
     
     
       34. The method of claim 33 wherein the first layer is a block copolymer comprising a polysiloxane chemical species and an acrylic chemical species. 
     
     
       35. The method of claim 33 wherein the printing member further comprises an intermediate layer between the first and second layers, and irreversible detachment is achieved by detaching the second layer from the intermediate layer.